Counting down circuit



O 7, 1952 E. P. SNYDER 'ET AL 2,613,318

coummc DOWN CIRCUIT Filed march 26,. 1946 0 CONTROL 3 l3 TUBE m 1 1 f BLOCKING DELAY GENERATOR CIRCUIT JAMES H. MULLIGAN, JR.

ELLERY R SNYDER Patented Dot. 7, 1952 I COUNTING nowuzcmonrrfl Ellery r. Snyder, United Statcs-Navy',Albany,"

Y STAT N. Y., and James H; Mulli an r.',United Sta-tes Navy, East Orange, N. J Application March'26, 194d r Claims: (Cl (Granted under the act of I 4 amended A'p'ril-30, 1928'; a

This invention relatesin generatto electrical frequency control circuits and in particular to a frequency divider circuit.

An object of this invention is to provide afrequency divider whichassiires accurate andposi- U "generating"-multivibrator; or ether suitablefde v ce is added to correct certain 'impositive action of pulse generator" 1-2 which occurs during sa 'Qfimtje interval of time-immediately following'athe "instant blocking generator 1-2 -returns to itsstabl'e tive frequency division at input signal frequensired output signal frequency. I

Another object of this invention is to provide'a frequency divider circuit in which the output si cies which are exact integralmultiples of thede- 'nal varies linearly to 'a maximum value'with' changes ininput frequency.

Other objects and features of thepresentin- -ven-tion will become apparent upona careful considerationof the following detailed description 'when taken together with the accompanying "drawings.

Fig. 1 is ablockdiagrtim ofo'ne embodiment ofthe invention, and I v Fig.2 is a detailed circuit diagram of Fig. l.

1 "In general, a frequency divider circuit con-- structed according to the teachings of the'invention, comprises, in part, a signalblocking circuit Land a delay circuit so connected thereto as toas- :sure positive and accurate frequencydivision overa Wide range of input signal frequencies.

Specifically; a preferred embodiment of the invention is disclosed in Fig. 1. Output signals of the source (usually a pulse source) over which frequency division is to be effected are impressed {across-a pair'of input terminals l3 and' "subse fqiiently appear at the output terminals -I4.*"'I"he "circuit components which perform frequency division are connected between the inputandoutput terminals-Band l4 and comprise-a-control 'tube 19,: delay circuit H and a blocking'pulse generator 12. "Control tube acts'essentially as 'a fs'witch whose operation is controlled by the blocking generator 12. The latter functions to "'rendertube iii non-responsive for selectable pejriods of timejduring'which, input signalsim- "pressed across terminals I3 are blocked from the circuit output terminals I4 with frequency division resulting. 'In thepreferred embodiment blockinggenerator I2 is of the self-returning .ttarcil 3, 1883, as v G. 751; T I

state. During 'this interval of time blocking genl erat or i2 is non-responsiveto trigger signals with the result that it will not drive back int its Lunstable state until-the next succeeding signal zat terminal 13. -This actioncausesthe outpuhsignalsat Mftoappear in pairs. I=f, howeverga delay is in'serted between the output of:control .tube

10 andthe application of the trigger signalcto 'blocking'generator t2 the latter will have time torecover-before the delayed trigger signal is .ap-

"plied thereto. Reliable operation-of the circuit will-thus result, provided, the delay'introduced by delay circuit ll is maintained at something less than the reciprocal of the maximumrepetition rate of the input pulses applied at terminals [3. It is, of course, to be'understood thatldelay circuit H is only necessary when the repetition period of the inputsignals is equallto, or an integral multiple of, the'blocking period of thergenerator'fl'.

-A detailed circuitdiagram of the preferredembodimen't of-the' invention is shown in.Fig. 2.

Tubes HA and I2B'comprise blocking generator l2; "The single stable state of this circuit exists when tube 2Ais'conducting andtube l2Bis nonconducting. To this end, grid of tubegHA is returnedthrough resistors 16 and H to a positive voltage supply and the cathode is. returned directly to'a negative voltage supply 28. ;T,ube

[2A 'will thus be quiescently strongly conductin with its "plate at virtually its cathode potential.

Then if cathode potential 28 ismade sufiiciently multivibrator type which contains a singular I stable state (if-operation but willmaintain for a selectable period of time, and in response'to a trigger signal, a second, but unstable state of .op-

eration. During the unstable stateof blocking generator l2, control tube 10 isrendered non-re-' sponsive and input signals applied at terminal -'are consequently blocked from the output terminalshi; 1

The trigger signal used to drive blocking genferator 12 into its unstable state is obtained from "the output of control tube Hi and for reasons hereinafter given in detail, is delayed by delay circuit H before application to the pulse genera- .torl2, Briefly, however, delay circuit H,;which may take theform of an artificial linepas pulse" jne'g'ative a direct'conductive connection, as here shown, can be made to grid 18 of tube 125. u'Ihe latter tube is shown as a pentode which permits the output signal, usedto block controltube I0,

to be taken directly from across screen resistance. '21. An obvious advantage of this arrangement -is that a'sharplydefined blocking signalisavailable at the screen of tube I2B since stray capacitances and their deleterious efiects-onpulse definition are at a'minimum ai'rthescreengrid.v .The

unstable stateof blocking generator 12 is ini- "tiated'b'y a negative 'sign'al'applied to the control gridof "tube HA. In response to this negative "signal tube HA is rendered non-conducting and j'tub'e 12B conducting in accordance .with-.\usual "multivibratoraction. Conduction by tube I23 and *nonconduc'tion by tube [2A prevails foria 'periodof time depending upon the'time constant formed by resistors 16, 11 and the plate to grid couplingcapacitorlfl. At the instant -tube"'l'2-B is driven into conduction, excessive screen grid current commences 'to'flowto thereby cause a I voltagejdrop to appearacross resistance 2 I. This "*"voltage drop is applied I through capacitor 30 to suppressongrid-fi of control tubeit. This action blocks plate current flow intube l to suppress all output signals at terminals l4. Thus for any given repetition rate of the input signal,

the frequency division which results is .a function of the period of the unstable state of blocking generator I2 and is adjustableby meansjof resistance [6.

After coupling capacitor 20 has '4 tube and operating to produce a signal delayed from theoutput of said control tube by an amount less than the interval between successive input signals, a self returning multivibrator connected charged up to a predetermined value through re- 12A is driven slightly positive as shown at point C in the accompanying oscillogram. It isduring thisintervaLwhen the grid of tube |2A is driven positive, that-the multivibrator is non-responsive :tdnegative triggering signals applied to grid l and for, this reason that delay circuit I l"'is includedbetween the outputof control tube l0 and the input to blocking generating circuit 12. In

. the practical embodiment of the invention a pulse generating multivibrator was employed at H with its pulse period adjusted so that the trailing edge of: its pulse occurred at the end of the'desired --delay interval to trigger blocking generator I2.

In choosing the control tube ID. a p ntode was :favored because such a tube permitted the simul- .itane'ous application of input signals to the control vgrid 2 1:and blocking signals to suppressor grid 25 without impairing the desired electrical isolation between a source at terminals 1 3 and the blocking generator l2. Furthermore such a tube permits the. use of self biasing (cathode resistor 23 and "capacitor 2 4) which provides for maximum sensitivity of thecircuit. At the start of the unstable period of the multivibrator i2, when tube [23 becomes conducting, tube! 0 is only blocked insofar as plate current is concerned and screen grid current may be maintained with the result that "the cathode bias may be maintained. 'lfo prevent the occurrence of an Ferroneous output signal at terminals [4 due to the suppressor grid 25 riding positive at the end of the blocking pulse a diode 22 is connected inshunt across thesuppressor return resistor -2 9.

Although we have shown and described only a invention it is to-be understood that many modi- 'certain and specific embodiment of the present fications are possiblethereof, therefore .-this invention is not to be limited Iexceptinsofar as necessitated by the spirit of the prior art and thescope of the appended claims i The invention described herein maybe manufactured and usedby or for the Government of the United States of America without the payment of any royalties thereon or therefon- *What is claimed is:

- "1. A frequency divider. comprising, a vacuum generating a. negative voltage pulse of controllable duration greaterthan the repetition period of the input pulse signal, and means for applying said negative voltage pulse to the suppressor grid of said tube to thereby render the latter nonresponsive for the duration of said negative voltage pulse. I

2. A frequency divider comprising, a control tube to which input signals are applied, a delay ,means connected tO the output of said control to said control tube and to the output from said delay means operative in response to an output signal from said delay means for rendering said 1' control tube non-responsive for a selectable interconnected to the suppressor grid of said tube and to the output of said delay means operative in response to an output signal from said "delay means for applying a negative voltage pulseof controllable durationto said suppressor grid to thereby render said. tube. non-responsive for an interval 'of time greater than the repetition period of the input pulse signal.

4 A frequency divider comprising, a vacuum tubehaving at least a suppressor and a control grid, said control gridbeihg adapted to receive input signals, means connected to the output o'f said tube for producing a signal which is delayed from the output of said tube by an amount less than the interval between successive input signals, a self returning multivibrator connectedto said last named means and operative in response to the output thereof for generating a negative voltage pulse of controllable duration and means comprising a diode connecting the output of said multivibrator to the suppressor grid of saidftub'e to thereby render said tube non-responsive for an interval of time greater than the repetition period of the input pulse signal.

; 55. A frequency divider comprising, an amplifier having input and output terminals with the input terminals arranged to receive the signals to be divided, a keyed pulse generator connected to said pulse generator for delivering a triggering signal to said pulse generator to initiate operation thereof, said time delay circuit providing a time delay; less than the interval between successive input signals to said amplifier, and said pulse generator providing a blocking voltage pulse having a duration greater than the repetition period of the signals to be. divided.

' ELLERY P. SNYDER.-

JAMES H. MULLIGAN, JR.

REFERENCES CITED The following references are of record in the file of this patent:

' :UNITED STATES PATENTS Number Name Date 2,212,558 Blumlein Aug. 27,1940 2,418,521 Morton et al Apr. 8,1947 2,419,570 Labin Apr. 29, 1947 2,468,058". Grieg Apr. 26, 1949 2,485,591 Grieg Oct. 25, 1949 v FOREIGN PATENTS Number e Country 7 Date 479,935 7 Great Britain Feb. 1'7, 1938 

